Anti-corrosion lubricating compound

ABSTRACT

AN IMPROVED HEAVY DUTY COATING COMPOSITION FOR PROTECTION AGAINST CORROSION OF METALLIC SUBSTRATES AND FOR LUBRICATION OF METALLIC PARTS COMPRISES A SUBSTANTIALLY UNIFORM MIXTURE OF AT LEAST ABOUT 40 WEIGHT PERCENT OF A SELECTED LEAD COMPOUND IN PARTICULATE FORM AND AN ESSENTIALLY HOMOGENEOUS GREASE-CONTAINING VEHICLE. THE VEHICLE COMPRISES A MAJOR PROPORTION OF GREASE, PEREFERABLY HEAVY DUTY GREASE, AND A MINOR PROPORTION OF LUBRICATING OIL, PREFERABLY HIGH PRESSURE LUBRICATING OIL. THE GREASE-CON TAINING VEHICLE IS NON-SEPARATING AND PREFERABLY THE GREASE IS PRESENT IN THE VEHICLE IN A WEIGHT RATIO TO THE OIL OF ABOUT 3:1. THE LEAD COMPOUND IS SELECTED FROM THE GROUP CONSISTING OF LEAD CARBONATE, LEAD SUBCARBONATE AND MIXTURES THEREOF.

United States Patent 3,7 84,472 ANTI-CORROSION LUBRICATING COMPOUND Stanley J. Caplan, Northridge, Califi, assignor to Accralube Company, Northridge, Calif.

No Drawing. Filed Oct. 26, 1971, Ser. No. 192,576 The portion of the term of the patent subsequent to Feb. 22, 1989, has been disclaimed Int. Cl. 010m 5/14 US. Cl. 252-25 Claims ABSTRACT OF THE DISCLOSURE An improved heavy duty coating composition for protection against corrosion of metallic substrates and for lubrication of metallic parts comprises a substantially uniform mixture of at least about 40 weight percent of a selected lead compound in particulate form and an essentially homogeneous grease-containing vehicle. The vehicle comprises a major proportion of grease, preferably heavy duty grease, and a minor proportion of lubricating oil, preferably high pressure lubricating oil. The grease-containing vehicle is non-separating and preferably the grease is present in the vehicle in a weight ratio to the oil of about 3:1. The lead compound is selected from the group consisting of lead carbonate, lead subcarbonate and mixtures thereof.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to lubricating compounds, and more particularly to such compounds providing special anticorrosion protection.

(2) Description of the prior art Conventional heavy duty lubricants and protective coating compositions commonly employ organic constituents such as organic acids, organic amines, organic phosphates, polyhydric alcohols and sodium and calcium sulfonates as active protective ingredients. Certain lubricants contain oxidation inhibitors such as alkyl phenols, thiophosphates and the like in concentrations of about 0.1 to about 1.0 percent by weight in a suitable vehicle. In certain instances, lead-type soaps and various sulfur, chlorine and phosphorus-containing organic additives are used with or without fillers such as graphite, molybdenum disulfide, talc, asbestos and the like as additives in thickened lubricants for heavy duty use.

Such protective coatings for metallic substrates attempt to either isolate the substrate, as by a relatively impervious film, or to coat the substrate with an inhibitor that protects the metal by a controlled release of inhibitor ions or the like, or both. However, the described anticorrosive type lubricants and coating compositions generally are subject to certain problems. 'For example, most of such lubricants are expensive and have a limited temperature range of efiective operation. When they break down under the stress of heat or friction they have a high residual ash content and may generate or release corrosive acids at a high conversion rate. Certain such lubricants and protective coating compositions exhibit low durability under extremely corrosive conditions such as salt water environments, high temperatures, high pressures and the like.

In order to overcome certain of the described deficiencies, attempts have been made in the past to add small amounts of metal base substances to the lubricants and coating compositions. Such substances are normally used in concentrations of the order of about 0.5-2 percent by weight, and in no instance in a concentration of more than about 10 weight percent. However, it has been found that the resulting compositions still are subject to relatively rapid breakdown in salt water use, nor do they exhibit optimum characteristics when used as lubricants in heavy duty machinery containing bearings and other components having close tolerances. In view of the deficiencies of the known lubricant and grease-base protective coating art, particularly with respect to use in heavy duty and highly corrosive environments, it would be desirable to provide a simple, inexpensive durable coating and lubricating composition.

Accordingly it is a principal object of the present invention to provide an improved heavy duty coating composition for protection of metallic substrates, which composition also has lubricating properties.

It is a further object of the present invention to provide an improved coating and lubricating composition for use in corrosive environments, which composition has increased resistance to breakdown and wear.

It is also an object of the present invention to provide a simple, inexpensive heavy duty coating and lubricating composition for protection of metallic substrates which composition is not subject to the production of acids or the like corrosive substances and which does not depend upon the incorporation therein of expensive organic antioxidants.

Further objects and advantages of the present invention will be apparent from a study of the following detailed description.

SUMMARY OF THE INVENTION In brief, the invention comprises a heavy duty coating composition for protection against corrosion of metallic substrates and for lubrication of metallic parts. The composition is in the form of a substantially uniform mixture of at least about 40 weight percent of a particulate compound selected from the group consisting of lead carbonate, lead subcarbonate and mixtures thereof and an essentially homogeneous grease-containing vehicle. The vehicle comprises a major proportion of grease, preferably heavy duty grease, and a minor proportion of lubricating oil, preferably high pressure lubricating oil. The grease-containing vehicle is non-separating and preferably the grease is present in the vehicle in a weight ratio to the oil of about 3:1.

The composition is capable of withstanding chemicals, salt water, acids, atmospheric corrosion, steam and high temperature and pressure while still providing suitable adhesion to metallic substrates and a lubricating effect at very low temperature. The composition is also effective as a rust inhibitor and serves as a protective coating against radiation, radio interference and corona.

LEAD COMPOUND Now referring more particularly to said coating composition, said composition includes at least about 40 percent, by weight of said composition, of the selected lead compound in particulate form, for example of commercial or reagent grade. Lead carbonate has the formula PbCO It comprises white, powdery crystals and is usually made by adding sodium bicarbonate to lead nitrate. Lead subcarbonate has the formula 2 PhCO -Pb(OH) and is a white non-crystalline powder. Either of these compounds or any mixture thereof can be successfully used in the present composition. It is preferred to use the selected lead compound in a particle size range of from about 30 to about 45 microns for best results. Physical limitations on the particle size of the selected lead compound will depend on the particular vehicle and the use to which the composition is to be put. Extremely small particles of the order of 5 microns or less in some instances are less eifective because they act as if they are plastic in nature and, as such, do not exert sufficient anti-corrosive effect. Moreover, very large particles are physically difficult to keep in a uniform suspension over an extended period of time and may also be incapable of forming the desired essentially continuous shielding layer of lead compound over the surface of the substrate to be protected.

The particles of the selected lead compound can be sized in any suitable way, as by grinding or the like, and act to effectively protect the substrate against corrosion over an extended period of time even in normally highly corrosive environments. Moreover, the composition has a sutable lubricating effect on the substrate to prevent galling and wear of the substrate. This protection against corrosion extends to such highly corrosive environments as sea water and the like. Apparently, although it has not been definitely established, the components of the greasecontaining vehicle portion of the composition act to coat the particles of the selected lead compound in a manner which permits the particles to slip past one another and function in a lubricating manner while still permitting their anti-corrosive effect to occur.

GREASE-CONTAINING VEHICLES The present composition also contains a grease-containing vehicle. The grease-containing vehicle comprises an essentially homogeneous uniform mixture of grease in a major proportion and lubricating oil in a minor proportion. However, it will be understood that in certain instances a different weight ratio of grease to lubricating oil can be used. For most purposes, however, only a relatively small amount of lubricating oil is present in the grease-containing vehicle. Both the lubricating oil and the grease may be any suitable commercially available product.

IJUBRICATING OIL In calculating the amount of lubricating oil in greasecontaining vehicle, that oil which is initially associated with and is part of the grease itself is not included. Thus, by lubricating oil in minor proportion is meant non-corrosive lubricating oil separately added in minor proportion to a suitable grease in formulating the present greasecontaining vehicle. Such lubricating oils should be present in a concentration in the grease insufficient to separate from the grease under conditions of normal usage but sufficient to act to lubricate the selected lead compound particles in the manner described above. It has been found for such purposes, concentrations of about 1 to about 30 parts of the lubricating oil to 99 to about 70 parts of the grease in the grease-containing vehicle are most suitable. Preferred ratios are about 1 part oil to about 3-4 parts by weight of the grease. Preferably, extreme pressure or high pressure lubricating oil is used. These are terms well-known to the oil lubricating art and are used in their usual sense. Extreme pressure and high pressure lubricating oils usually are petroleum grade oils which contain small concentrations, usually about 0.1-0.5 percent by weight of additives which act at high temperatures to form high melting point inorganic lubricant films to avoid massive welding and breakdown of lubricated substrates. Such additives may comprise, for example, sulfur, chlorine, phosphorus or the like compounds in suitable organic form. These compounds may provide low shear strength areas or act as fluxing agents for contaminated metallic surfaces to prevent welding under pressure. Gear oil which may contain tallow or the like to minimize scufling and wear during use can also be utilized as the lubricating oil. It will be understood that for the purposes of the present invention any suitable lubricating oil may be used, such as gear oil, high pressure or extreme pressure lubricating oil, or standard lubricating oil of any suitable viscosity, for example 20-30 SAE, with or without additives.

4 GREASE The grease in the vehicle may be any suitable grease known in the lubricating and protective coating art which is non-corrosive in nature and capable of withstanding elevated temperature and pressure conditions. What is termed heavy duty grease and is well known as such in the art is preferred. Chassis grease or other grease can be used. Such grease may be, for example, a lubricating petroleum oil suitably thickened with a gelling agent such as a fatty acid soap of lithium, calcium, sodium, aluminum or barium or a mixture thereof. The fatty acid may be, for example, oleic acid, palmitic acid, stearic acid or other carboxylic acid derived from tallow, hydrogenated fish oil, castor oil or the like. Certain synthetic greases can be used, for example, those diester greases from diester oils such as di(Z-ethylhexyl) sebacate. Silicone grease and various radiation-resistant greases can be used.

The grease should have a sufficiently high viscosity so that when utilized in a suitable mixture with the added lubricating oil, it provides both a lubricating effect and an adhesive protective coating effect when disposed on the metallic substrate to be protected. It will be obvious to those who are skilled in the art that a wide range of viscosities for the grease and the resulting grease-containing vehicle can be employed, depending on the particular applications of the composition. Petroleum oils are present in over about 99% of the greases commonly used as protective coatings. The petroleum oil in such greases usually has an SAE rating of about 20-30 with a 100 F. viscosity of about 200-600 SUS. Some lubricating oils also contain amines, phenolics, phosphates, sulfur, selenium and the like inhibitors, usually at 0.1-0.5 weight percent concentration therein. If desired, they can be used as the lubricating oil portion of the grease or the lubricating oil component of the grease-containing vehicle.

It will be understood that both the grease and the added lubricating oil in the grease-containing vehicle must be substantially non-corrosive in character and capable of providing the desired viscosity for the vehicle and also the desired lubricating effect for the substrate and the particles of the selected lead compound. Neither the grease nor the lubricating oil need contain additives although additives are not excluded from the scope of this invention. It is within the skill of one versed in the art on the basis of this specification to readily provide suitable compositions including the grease and the lubricating oil in proper mixture.

PREPARATION OF COATING COMPOSITION The grease-containing vehicle is provided by mixing together, to form the essentially homogeneous non-separating mixture, the selected grease together with the added lubricating oil in a proper mixture. The mixing may be, for example, mechanical mixing at low or relatively high speed, depending upon the viscosity of the grease-containing vehicle. As indicated above, such vehicle preferably contains a ratio, by weight of the vehicle, of added lubricating oil to grease of about 1:3-4. It is also a part of the present invention that the vehicle can contain the added lubricating oil in major proportion and the grease in minor proportion, but this is unusual.

In accordance with the present invention, the particles of the selected lead compound are blended together with the grease-containing vehicle to provide a uniform, stable, non-separating mixture. The blending may involve any suitable blending procedure to provide the uniform mixture, as by mechanical stirring or the like. The lead compound is present in the coating composition in a concentration of at least about 40 percent, by weight of the coating composition, and preferably not more than about or weight percent, although higher concentrations can be used, if desired. A preferred range is 73-76 weight percent, with the oil 6-7 percent and the grease 17-21 percent. It has been found that concentrations of. the

selected lead compound of less than about 40 percent, by weight, of the coating composition of the present invention are usually ineffective to achieve the desired results. The practical upper limit of concentration of the selected lead compound will vary according to the lead compound particle size and the type of grease-containing vehicle employed, i.e. it will be that highest concentration which can still be kept in uniform suspension with sufiicient vehicle present to properly suspend, support and lubricate the same for protective film forming. Concentrations of the related lead compound particles will above 80 weight percent concentration, e.g. about 90 weight percent or more may have a tendency to disrupt the continuity of a film of the composition so as to depreciate its lubricating purposes and/ or anti-corrosion characteristics over an extended period of time. Moreover, it is expensive. Preferably, the coating composition consists essentially of the selected lead compound and the grease-containing vehicle in the indicated concentrations, although the presence of other ingredients, such as thickening agents, inhibitors, etc. is not precluded. Such inhibitors and thickening agents have been previously described.

Certain features of the present invention are further illustrated in the following specific examples.

EXAMPLE I An improved lubricating and anti-corrosive coating composition suitable for heavy duty use in marine and other environments is provided by mixing together the following constituents as set forth in Table I below:

TABLE I Ingredients: Percent by weight Lead carbonate (30-45 micron average diam.) 7 6 Heavy duty commercial grease 18 High pressure commercial oil 6 The above-indicated composition of Table I is provided by first mechanically blending together at low speed the heavy duty grease and the high pressure oil and then adding to the resulting mixture to provide the uniform, essentially non-separating composition of the present invention, the particles of leadcar'bonate while continuing the mechanical blending. Lead carbonate in crystalline powder form can be agglomerated, then sized through a standard 325 mesh screen. A parallel composition to that of Table I and having comparable properties is obtained when commercial lead subcarbonate is substituted for the lead carbonate, when axle grease is substituted for the heavy duty grease and when SAE .30 lubricating oil is substituted for the high pressure oil.

The composition of Table I, when spread as a ,5 inch thick film on panels of cold rolled .steel previously acid cleaned and prepared as per federal test standard 141 and exposed, after coating, to immersion in an aqueous solution containing 20 percent by weight of sodium chloride, at a temperature of 150 F.'for 24 hours with mechanical stirring demonstrates essentially a low loss of film thickness, and no corrosion of the substrate in contact with the film.

When the identical procedure referred to above is followed in testing parallel samples A, B, C and D certain important features are discernible. Sample A contains only the grease-containing vehicle, i.e. the grease and oil of Table I but no lead carbonate or lead subcarbonate. Sample B contains 70 percent by weight of the vehicle (grease and oil) of Table I and 30 percent by weight of the lead carbonate. Sample C contains 55 percent by weight of the vehicle (grease and lube oil) and 45 percent by weight of the lead carbonate, while Sample D contains 45 percent by weight of the vehicle and 55 percent by weight of the lead carbonate. All ingredients are the same ones listed in Table I. When tested for film adhesion under the same conditions specified above for the composition of Table I, over 80 percent of the film is removed when no lead carbonate is present (Sample A). About percent of the film is removed when the concentration of the lead carbonate in the composition is only about 30 weight percent (Sample B). However, Samples C and D containing respectively, 45 and 55 weight percent of the lead carbonate exhibit an average film loss of only about 50 percent. Accordingly, it is demonstrated by the above test that the adhesion of the composition to the metal under corrosive conditions is substantially increased through the use of high concentrations of the lead carbonate in the composition. Parallel tests substituting subcarbonate for the lead carbonate yield comparable results.

EXAMPLE II Parallel test samples of the coating composition of the present invention are provided for testing in the manner set forth in Example I, but containing the following constituents:

TABLE II Lead carbonate, percent by Percent by weight weight (3045 micron average Lubricating oil Sample number diameter) Axle grease (gear oil) In each instance, Samples 1-9 are prepared by blending together the individual constituents, that is, the grease, the oil and the lead carbonate to provide a uniform homo geneous mixture. The lead carbonate has an average particle size of up to 50 microns in diameter. Each of Samples 1-9, inclusive, is tested by spreading it as a inch thick film on the surface of a clean cold rolled sheet panel of steel and then immersing the coated panel in an aqueous bath containing 20 percent by weight of sodium chloride, at a temperature of 150 F. The plate is held in the bath .for a period of 200 hours with stirring of the bath through the use of a mechanical stirrer. Under the foregoing circumstances, the compositions represented by Samples 1-4 exhibit substantial corrosion of the steel panel with removal of all or a substantial portion of the film. The panels coated with Samples 5-9 exhibit no corrosion. Samples 8 and 9 show the thickest retained protective film.

EXAMPLE III Parallel samples are provided in the manner described in Example I but ultilizing the composition set forth in Table III below:

TABLE III Percent by weight Commercial Commercial Commercial a heavy duty high pressure Sample number subcarbonate grease lube oil Each of Samples 10-17, inclusive, is tested in accordance with the test described in Examples I and 11, except 7 that the test is continued at 150 F. for a total of approximately 500 hours. Table 1V below indicates the results:

TABLE IV Extent of visible corrosion on panel Thickness of resulting interface with film film at end of test Sample number Table IV indicates that when the lead subcarbonate concentration falls below 40 weight percent, corrosion occurs. None occurs in the 40-85 weight percent range, but some thinning of the protective film is exhibited. Sample 13 shows the greatest retention of film and therefore the greatest anticorrosive etfect.Compositions within the critical weight range for the subcarbonate are more easily pumpable and show low temperature suitability to a greater degree than the usual anti-corrosive lubricants. This is also the case when the lead carbonate is used in place of or in addition to the lead subcarbonate. All mixtures of lead carbonate and lead subcarbonate perform equally as well as either compound by itself in the coating composition.

Tests measuring the lubricity as well as the anti-cormsive protective nature of the coating composition indicate that the present composition performs in a superior manner. Improved anti-galling and anti-seizure protection is provided by the present coating composition for bearings and other moving parts of heavy duty machinery exposed to salt spray and the like, in contrast to other coating and lubricating compositions, even those containing up to weight percent of lead compounds and/or organic antiwear substances.

As an example of the superior lubricating and anti-corrosion properties of the present composition, it is used as the lubricating grease in a Ford Model 4500 tractor equipped with a Model 755 backhoe and a Model 740 loader. The grease is applied by pumping into the grease fittings at the points of stress and strain of the combination unit and use of the composition results in a considerable reduction of failure and wear of the components so lubricated. The composition used is that set forth in Table I above, prepared as described in connection therewith.

Various changes can be made in the present composition, for example, in the grease component, or in the particular lubricating oil, the overall viscosity of the grease and oil. All such changes in the present composition, its components and in the method of making the composition as are within the scope of the appended claims form a part of the present invention.

What is claimed is:

1. An improved heavy duty coating composition for protection against corrosion and for lubrication of metallic substrates, said composition comprising a substantially uniform mixture of an essentially homogeneous greasecontaining vehicle which comprises grease in major proportion and lubricating oil in minor proportion and at least about 40 percent, by weight of said composition, of lead compound in particulate form, said lead compound being selected from the group consisting of lead carbonate, lead subcarbonate and mixtures thereof.

2. The composition of claim 1 wherein said grease comprsies heavy duty grease, and wherein said lubricating oil comprises high pressure lubricating oil.

3. The coating composition of claim 1 wherein said lead compound comprises lead carbonate.

4. The coating composition of claim 2 wherein said lead compound consists essentially of lead carbonate.

5. The coating composition of claim 1 wherein said lead compound comprises lead subcarbonate.

6. The coating composition of claim 2 wherein said lead compound comprises lead subcarbonate.

7. The coating composition of claim 4 wherein said lead carbonate is in a concentration of about 73-76 weight percent in said composition and has an average particle diameter of about 30-45 microns, wherein said lubricating oil is present in said grease-containing vehicle in a concentration of about 6-7 percent of said coating compositionand said grease of said vehicle is present in a concentra tion of about 17-21 percent of said coating composition.

8. The coating composition of claim 6 wherein said lead subcarbonate is in a concentration of about 73-7-6 weight percent in said composition and has an average particle diameter of about 30-45 microns, wherein said lubricating oil is present in said grease-containing vehicle in a concentration of about 6-7 percent of said coating composition and said grease of said vehicle is present in a concentration of about 17-21 percent of said coating composition.

9. The coating composition of claim 7 wherein said coating composition consists essentially of said lead carbonate of said grease-containing vehicle.

10. The coating composition of claim 8 wherein said coating composition consists essentially of said lead subcarbonate and said grease-containing vehicle.

References Cited UNITED STATES PATENTS 3,642,625 2/1972 Caplan 252-25 2,285,452 6/ 1942 Merkle 252-25 2,889,279 6/ 1959 Carlyle et a1. 252l8 3,271,309 9/1966 Caruso 25225 FOREIGN PATENTS 754,007 8/1956 Great Britain 252-18 PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner US. Cl. X.R. 25 2-1 8 

